(1). After the intraperitoneal injection of pulped mouse foetus and placenta into mice with implanted carcinomata, disappearance of the implanted tumour occurred in 13,7 pCt. of the experiments made, arrest of growth taking place in 10,6 pCt. of the experiments. In 71,2 pCt. the growth of the tumour was not interrupted. (2). After previous exposure to the temperature of solid CO2, the intraperitoneal injection of pulped mouse foetus and placenta was not observed to affect the growth of implanted mouse carcinoma. (3). After intraperitoneal injection of pulped mouse carcinoma, tumours developed in the peritoneal cavity as a rule. The implanted carcinomata, present at the time of injection, in some experiments continued to grow, in other experiments became diminished in size, ultimately disappearing if the animal survived sufficiently long. (4). The injection of pulped mouse carcinoma, previously exposed to the temperature of solid CO2, was found to inhibit the growth of implanted carcinomata in about one third of the mice injected.